This invention relates to earth satellites that operate in inclined, elliptical orbits and that use infrared earth sensors (ES) for satellite roll and pitch attitude reference determinations. These sensors utilize a plurality of scan lines, which are areas of the earth viewed by a satellite from which the sensor detects infrared radiation from the earth (see FIG. 1). The length of these scan lines over the earth view is utilized by the satellite Attitude Control Subsystem (ACS) to determine the position of the satellite. The infrared data from the scan lines sometimes experience undesirable disturbances, arising from a rapid change in the measured infrared radiation as the ES scan lines traverse certain regions on the earth such as, for example, polar regions, particularly during polar winter. These disturbances, referred to as earth radiance disturbance events (ERGD's), alter the magnitude of the scan lines inputted to the satellite's ACS, causing satellite pointing errors in the pitch and roll axes. Such errors may lead to strain on satellite operations, or even loss of satellite/earth contact. The systems and methods of this invention determine, predict the geographical boundaries and time periods where and when ERGD's occur, and mitigate or avoid such ERGD's.
This invention relates, in part, to satellite systems disclosed in the following patents and patent publications:
U.S. Pat. No.TitleIssue Date6,564,053Efficient High Latitude ServiceMay 13, 2003Area Satellite Mobile Broad-casting Systems6,023,616Satellite Broadcast ReceiverFeb. 8, 2000System5,864,579Digital Radio Satellite AndJan. 26, 1999Terrestrial Ubiquitous Broad-casting System Using SpreadSpectrum Modulation5,794,138Satellite Broadcast SystemAug. 11, 1998Receiver5,592,471Mobile Radio Receivers UsingJan. 7, 1997Time Diversity To Avoid ServiceOutages In Multichannel BroadcastTransmission Systems5,485,485Radio Frequency BroadcastingJan. 16, 1996Systems And Methods Using TwoLow-Cost Geosynchronus SatellitesAnd Hemispherical CoverageAntennas5,319,673Radio Frequency BroadcastingJun. 7,1994Systems And Methods Using TwoLow-Cost Geosynchronus SatellitesEPO PatentTitleDate Of Pub.EP 0 959 573 A2System For Efficiently BroadcastingNov. 24, 1999Via Satellite ToEP 990303823Mobile Receivers In Service AreasAt High LatitudeInt'l. Pub. No.TitleIntl. Pub. DateWO 01/33729 A1Method And System For ProvidingMay 10, 2001Geographic Specific Services InA Satellite Communications NetworkWO 01/33720 A3Method And Apparatus ForMay 10, 2001Selectively Operating Satellites InTundra Orbits To Reduce ReceiverBuffering Requirements For TimeDiversity Signals
Each of these patents and patent publications is incorporated herein by reference as though fully set forth here.